DESCRIPTION (provided by investigator): This study will employ new research design and analytical methods to explore the role that environmental tobacco smoke (ETS) may play in the behavior problems and sleep patterns of children. The study uses children enrolled in a double blind, placebo controlled trial (R01-HL6573101) investigating the benefits of ETS exposure reduction on asthma symptoms. The 232 children, aged 6-11 years, have doctor-diagnosed asthma and are exposed to at least 5 cigarettes per day in their homes. Intervention to reduce exposure to ETS consists of placement of 2 high efficiency air filtration devices (HEPA-CPZ) or inactive (placebo) units in the home for a period of 12 months. Acute and chronic biological measures of ETS exposure (serum and hair cotinine) and air nicotine are collected at baseline, 6 months, and 12 months, to assess exposure to ETS. Asthma symptoms and severity are monitored throughout the study period. The proposed study utilizes additional (non-funded) measures collected at baseline and study termination to assess child behavior changes (rated by parents and teachers), child sleep habits, and qualities of the care-giving environment. This study will be the first double blind, randomized, placebo-controlled trial, utilizing passive measures, to explore the role of ETS in the development of behavior problems and sleep patterns among children with asthma. We request 24 months of support with which to explore this data. We will explore the direct relationships of ETS on behavior and sleep problems through an intention-to-treat analysis of the randomized trial. We will additionally explore the potential causal pathways from ETS exposure to behavior and sleep problems, with consideration of mediating variables such as asthma severity and characteristics of the care-giving environment, buy employing structural equation modeling techniques. We will focus on the following aims: 1: To explore the relationship between ETS exposure, as measured by biomarkers of exposure, and behavior problems in a cohort of children with asthma who are exposed to ETS in their homes. 2: To explore the relationship between ETS exposure, as measured by biomarkers of exposure, and sleep patterns in a cohort of children with asthma who are exposed to ETS in their homes. 3: To explore the pathways between ETS exposure and disturbances in child behaviors and sleep patterns with consideration of mediating factors such as asthma severity and characteristics of the care-giving environment using structural equation modeling techniques that have never been used in examining the effects of ETS. This proposed analysis offers a unique opportunity to explore the causal pathway between exposure to ETS and behavior and sleep problems of children through data collected during a rigorous double blind, randomized trial to reduce ETS exposure among children with asthma.